In the past, the applicant has proposed an opening and closing valve that can be attached to a discharge port of a liquid container. As described in Japanese Utility Model Application Publication No. H05-083560, the opening and closing valve thereof is provided with a base end part having an inflow port for a liquid in a container, an operation lever for opening and closing the valve, a valve body which is opened and closed by rotating the operation lever, and a discharge port which communicates to the inflow port when the valve is opened. Furthermore, a male screw which helically engages with a female screw formed at the discharge port of the container is formed at the base end part where the inflow port is formed at the base end.